Mixing C and C++?

[Erik de Castro Lopo]

Hi all,

I have an project that uses automake, autoconf and libtool and for one
of the generated binaries, I'm trying to mix C and C++, but automake is
giving me the following error:

    tests/Makefile.am: object `cpp_test.$(OBJEXT)' created by `cpp_test.cc'
    and `cpp_test.c'

My project does have a cpp_test.cc but does not contain cpp_test.c.
The C++ file has a single public extern "C" function that is called
from the C code.

Any clues? I've tried searching Google, but this error message is 
particularly difficult to Google for.

Cheers,
Erik
-- 
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Erik de Castro Lopo
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"C++ is a language strongly optimized for liars and people who
go by guesswork and ignorance." -- Erik Naggum
-- 
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Erik de Castro Lopo
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"Reality is just a crutch for people that can't handle CyberSpace!!"
- Hank Duderstadt